The project is to investigate alterations of size and number of glutamatergic and GABAergic synapses in hippocampal CAl and CA3 dendritic regions following an episode of cerebral ischemia in rats. The total numbers of synapses between ischemic and control rats will be determined from EM micrographs using stereological procedures, 3-D reconstructions from serial sections and the facilities and expertise of the NCMIR. Light microscopic analysis of glutamate and GABA receptor distributions will be analyzed using the confocal microscope. The goal of this project is to understand the reconstruction of brain synapses following cerebral ischemia. Blocks of hippocampus from two animals: 1 control and 1 subject to 15 min. of ischemis followed by 4 hr reperfusion, have been prepared for the EM analysis. We are currently evaluating software packages for sterologyical analysis to be installed at the NCMIR.